Research questions of central interest are possible relations between the attributes and experiences of parents, and adverse reproductive outcomes. Attributes of parents include age, prior reproductive experiences, medical conditions including genetic disorders, demographic background; experiences include habits (cigarette smoking), home and job exposures to chemicals, therapeutic drugs, contraceptives. The adverse reproductive events are the event of spontaneous abortion estimated as an odds ratio, in a case-control study and the event at given stages of gestation; the karyotypic character of the abortus (euploid, trisomic, monosomic, triploid, tetraploid, translocation, mosaic, other); the morphology of the abortus beyond 28 weeks. There is also interest indifferences in sex ratio, and differential findings for male and female offspring. Findings established by the study include: an excess risk for spontaneous abortion (and in particular, for euploid conceptions) among women who smoke during pregnancy, for those drinking in moderate amounts of alcohol during pregnancy, and for those whose conception occurred while using an intrauterine device; for women over 35 years; for women using heroin or methadone and women with a history of repeat abortions. The risk was not raised for those who had experienced a single previous induced abortion, nor for those who ingested saccharine.